Date of Award
August 2024
Degree Type
Thesis
Degree Name
Master of Science
Department
Biomedical Sciences
First Advisor
Troy Skwor
Committee Members
Ryan Newton, Elizabeth Liedhegner
Abstract
Aeromonas spp. are recognized as emerging human pathogens associated with gastroenteritis, wound infections, and bacteremia. Considering its ubiquitous nature in aquatic environments, many of these diseases arise from direct or indirect aquatic exposure. However, comparisons of Aeromonas populations among environmental sources compared to clinical populations are rarely reported. Therefore, our objective was to compare environmental Aeromonas populations from treated wastewater effluents and neighboring recreational beaches to clinical strains from the same geographical locations to assess the potential health risk. Environmental Aeromonas isolates were acquired from beaches and post-chlorinated wastewater (POC) using ampicillin dextrin agar with vancomycin and irgasin (ADA-VI). Antibiotic susceptibility was determined using Kirby-Baur disk diffusion with subsequent analysis of ARGs using PCR. To assess the clinical relevance of environmental isolates, we identified the species and virulence potential. Species were identified using gyrB PCR amplification and sequencing of subpopulations of clinical, POC, and beach isolates. Our findings identified clinical and POC populations as the most similar antimicrobial resistance (AMR) profiles except for nalidixic acid resistance (10.5% to 42.9% respectively), while beach isolates had the highest antibiotic susceptibility. Statistical differences among sources (P<0.05) were observed for sulfamethoxazole-trimethoprim, tetracycline, gentamicin, overall AMR, and multi-drug resistance. Environmental Aeromonas spp. also encoded similar AMR genes (sul1/2, tetE, OXA, and TEM) to clinical populations. Among all sources, thirteen species were identified, with the most prevalent beach (A. veronii) and POC (A. hydrophila) species, resembling Aeromonas species common in the clinic. To determine their potential to cause disease, we assessed the presence of ten virulence genes and cytotoxicity of filtered supernatants against human epithelial cells. Although cytotoxic enterotoxin (act) and hemolysin (hlyA) were more common among clinical populations (P<0.05), overall similar virulence profiles existed for clinical, POC, and beach populations. Furthermore, act was the only virulence gene strongly associated with the cytotoxic phenotype. In conclusion, strong similarities in antibiotic resistance, species, and virulence factors between environmental and clinical isolates suggest beaches and POC wastewater serve as potential sources of clinical infections.
Recommended Citation
Bojar, Brooke, "ANTIBIOTIC RESISTANCE AND VIRULENCE PROFILES OF AEROMONAS POPULATIONS FROM BEACH AND POST-CHLORINATED WASTEWATER COMPARED TO CLINICAL ISOLATES IN MILWAUKEE, WISCONSIN, USA" (2024). Theses and Dissertations. 3555.
https://dc.uwm.edu/etd/3555